Flesh-Eating Parasite Jumps U.S. Border

A deadly flesh-eating livestock parasite just crossed back into the United States for the first time in six decades, and Texas ranch country is once again on the front line.

Story Snapshot

A federal lab has confirmed New World screwworm in a 3‑week‑old calf in Zavala County, Texas, the first U.S. case since the 1960s.
The parasite’s maggots eat live flesh in open wounds of cattle, wildlife, pets, and even people, often leading to crippling injuries or death.
USDA and Texas officials have launched quarantines, surveillance, and sterile-fly releases, calling this a serious livestock biosecurity event.
Experts say the food supply remains safe for now, but the economic stakes for cattle country are enormous if the pest spreads.

What Exactly Hit This South Texas Calf?

The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) confirmed New World screwworm larvae in a 3‑week‑old calf in Zavala County, after testing at the National Veterinary Services Laboratories in Ames, Iowa.^[1]^[2] The maggots were found in the calf’s umbilical area, a classic target because the open navel wound offers the perfect entry point.^[1]^[2] To date, federal officials report no additional detections in U.S. livestock, wildlife, or pets tied to this case.^[1]^[2]

Texas A&M specialists describe the New World screwworm as a parasitic fly whose females lay eggs in open wounds of warm‑blooded animals, where the hatched larvae burrow into and feed on living tissue rather than dead flesh.^[1] This active consumption of live muscle and skin can rapidly enlarge wounds, trigger severe infection, and, without prompt treatment, kill the host animal.^[1] Texas wildlife officials similarly warn that infestations can strike newborns and other animals wherever a wound or body opening exists.

Why Ranchers Are Right To Take This Seriously

Texas A&M reports that since 2023 the screwworm has re‑established itself north of the Panama Canal and moved as far north as Veracruz, Mexico, with more than 6,500 cases reported in 2024.^[1] That steady march toward the border has put every South Texas rancher on edge, knowing how quickly this parasite once spread across the southern cattle belt before its eradication in the 1960s.^[1]^[2] The confirmed Texas calf now marks the crossing of a line ranchers hoped would hold.

Texas Farm Bureau guidance to producers stresses that early detection and rapid reporting are critical, urging ranchers to isolate suspect animals, call a veterinarian immediately, and report cases to the Texas Animal Health Commission without delay.^[2] Under the protocol described by Texas A&M, veterinarians are legally required to collect and submit larvae from suspected screwworm cases to the USDA’s National Veterinary Services Laboratory for definitive identification.^[1] That formal chain of custody underscores that Washington treats even a single detection as a high‑stakes biosecurity issue.^[1]^[2]

How The Federal Response Is Unfolding Under Trump’s USDA

USDA’s announcement makes clear that officials are not treating this as a minor curiosity; they have activated quarantine-style movement controls, stepped‑up surveillance, and sterile insect releases around the affected zone in South Texas.^[1]^[2] The agency says it has already deployed thousands of traps across the southern tier since early 2025, generating tens of thousands of samples and wildlife checks that came back negative until this calf.^[2] That groundwork allows a faster, more targeted response now that a positive case has appeared inside U.S. borders.^[1]^[2]

Containment efforts include restricting animal movements in and out of the immediate area, mapping a control zone, and releasing large numbers of sterile male screwworm flies to overwhelm any wild breeding population.^[1] This “sterile insect technique” was the backbone of the original eradication campaign that pushed the pest all the way into Central America decades ago.^[1] Federal officials emphasize that the strategy is designed to crush any emerging population quickly, before it can establish in Texas cattle herds or native wildlife.^[1]

Real Threat To Herds, Limited Risk To Food Supply

Both USDA and state leaders are drawing a sharp line between herd health risk and food-safety risk, a distinction often lost in sensational headlines about “flesh‑eating worms.” USDA’s Food Safety and Inspection Service notes that screwworms do not infest meat, fruits, vegetables, or other food products.^[1]^[2] Any infested animal that moved into the inspected meat chain would show clear evidence at slaughter, and contaminated carcasses would be barred from the food supply.^[1]

A case of New World screwworm has been confirmed in the umbilicus of a 3-week-old calf in Zavala County, Texas by the @usda_aphis. https://t.co/ZtUXyXwAeV

— AVMA (American Veterinary Medical Association) (@AVMAvets) June 4, 2026

Even so, the economic risk to the cattle sector is substantial if the parasite spreads beyond the initial zone. Texas A&M highlights that screwworm infestations inflict heavy economic losses through animal deaths, treatment costs, and trade disruptions when countries tighten restrictions on livestock and animal products.^[1] Industry outlets covering the Texas case urge producers across the southern United States to stay vigilant, noting that the most recent Mexican detections were already within a few hundred miles of the border before this incident.^[3]^[4]